The present invention relates to a die system for producing blanks from a sheet of material. More particularly, the present invention relates to an apparatus and method for punching corner scrap material from the sheet of material in a predetermined pattern to define a grid of blanks on the sheet of material, scoring the blanks in a predetermined pattern, and then severing the sheet of material to form the blanks without producing any additional scrap material.
In recent years, the popularity of heat-and-serve foods has increased. With the increased popularity of these heat-and-serve foods, the need for disposable trays made from inexpensive materials such as paper has also increased. These disposable trays are formed by stamping blanks of material inside a die press.
One problem associated with the production of blanks from a sheet of material is that a large amount of scrap material is produced. Therefore, a substantial amount of the sheet of material is wasted. The cost of this wasted material is substantial, especially for a continuously running blank-forming device.
Blanks are often unevenly or nonuniformly scored by conventional blank forming devices. During formation of trays from scored blanks, blanks with unequal or nonuniform scoring are more likely to be torn as they are stamped between male and female dies of the die press.
Punches used in conventional blank forming devices must be replaced when they become worn. In addition, replacing or sharpening the punches can be difficult, time consuming, and expensive. Therefore, a conventional blank forming machine must be shut down for a substantial time during replacement or sharpening of the punches.
One object of the present invention is to reduce the amount of scrap material generated during the process of cutting a sheet of material to provide a plurality of separate blanks suitable to be stamped in a die press to convert each blank into a disposable tray.
Another object of the present invention is to provide uniform scoring on a surface of the blank to facilitate the formation of compartments in the blank and to reduce the likelihood that the blank will be torn during stamp-forming of the blank in a die press.
Yet another object of the present invention is to provide a mechanism for severing the sheet of material, which mechanism is less expensive to manufacture and easier to maintain than conventional punches of the type used to form blanks from a sheet of material.
According to the present invention, a die system is provided for producing blanks from a sheet of material. According to one aspect of the invention, the die system includes means for punching corner scrap material from the sheet of material to define an array of interconnected blanks arranged in a grid of rows and columns in the sheet of material. The die assembly also includes blanking means situated downstream from the punching means for piercing the sheet of material in a predetermined pattern to cut blanks of a predetermined size from the sheet of material without producing any additional scrap material.
The blanking means includes a die plate having a support surface for supporting the sheet of material. The die plate is formed to include first and second blank discharge apertures positioned in a spaced apart relation. The first and second blank discharge apertures are aligned with a single row of blanks and alternate columns of blanks in the sheet of material.
This aspect of the invention advantageously reduces the amount of scrap material produced during formation of blanks from a sheet of material. Because the production of blanks from sheet material is typically a high volume job in which the blank forming machine runs continuously, the reduction in the amount of paper wasted per year by the present invention is substantial. This reduction in the amount of paper wasted translates directly into cost savings during the blank production process.
According to another aspect of the present invention, the die assembly includes means for simultaneously scoring a trailing portion of a first row of blanks and a leading portion of a succeeding row of blanks on the sheet of material moving through the die assembly. The scoring means scores a first predetermined pattern only on the trailing portion of the first row of blanks while simultaneously scoring a second predetermined pattern only on the leading portion of the succeeding row of blanks.
The scoring means is located between the punching means and the blanking means in a center portion of the die assembly spaced apart from an entry region and an exit region of the die assembly. By locating the scoring means in substantially the center portion of the die assembly, the scoring means advantageously provides more uniform scoring on the blanks than conventional blank-forming devices. This uniform scoring facilitates formation of trays from the blanks by a die press and reduces the risk that the blanks will be torn by the die press.
According to yet another aspect of the invention, the die assembly includes first and second die shoes and means for providing reciprocating movement of the first and second die shoes relative to each other. The die system includes a first shearing edge situated on the second die shoe and a knife member mounted to the first die shoe. The knife member has a second shearing edge for engaging the first shearing edge to cut the sheet of material. The knife member is mounted on the first die shoe so that the second shearing edge is oriented at a predetermined, nonparallel angle with respect to the first shearing edge so that "scissors" means is created by the first and second shearing edges for severing the sheet of material upon relative movement of the first and second die shoes.
The knife member is formed to include a plurality of cutting edges and is mounted to the first die shoe to position a selected one of the cutting edges over the sheet of material to sever the sheet of material upon relative movement of the first and second die shoes. Advantageously, when the selected cutting edge that is positioned over the sheet of material becomes dull, the knife can be rotated relative to the die shoe on which it is mounted to position another selected cutting edge over the sheet of material so that it can be used to sever the sheet of material. Therefore, the amount of machine down time required for maintenance is reduced by this aspect of the invention.
According to still another aspect of the present invention, a method is provided for progressively converting a sheet of material moving along its length in a downstream direction through a die assembly into a plurality of sets of blanks. The method includes the steps of punching corner scrap material from the sheet of material to define an array of interconnected blanks arranged in a grid of rows and columns on the sheet of material. Each row of blanks has a leading portion adjacent to a trailing portion of a downstream row and a trailing portion adjacent to a leading portion of an upstream row. The method also includes the step of simultaneously scoring a trailing portion of a first row of blanks and a leading portion of an adjacent succeeding row of blanks at the same time. The method further includes the step of piercing the sheet of material in a predetermined pattern to form blanks of a predetermined size from the sheet of material without producing any additional scrap material.
Additional objects, features, and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of a preferred embodiment exemplifying the best mode of carrying out the invention as presently perceived.